Continuous time sigma-delta analog-to-digital converter with stability
View Patent ↗A continuous time sigma-delta analog-to-digital converter (CT ΣΔADC) including an integrator, which includes an operational amplifier having at least one input terminal that receives an input signal, a feedback mechanism operatively connected to the operational amplifier, at least one capacitor coupled to the operational amplifier and the feedback mechanism, a reset switch coupled to the at least one capacitor, the operational amplifier, and the feedback mechanism, and a single directional voltage-to-current converter coupled to the input terminal. The single directional voltage-to-current converter translates a differential signal voltage only to a differential signal current. The reset switch resets the feedback mechanism. The single directional voltage-to-current converter behaves a one-directional resistor. The integrator prevents current generation when there is a non-linear disturbance at the input terminal of the operational amplifier. The single directional voltage-to-current converter clips an input current that exceeds a threshold value.
1. A continuous time sigma-delta analog-to-digital converter (CT ΣΔADC) comprising an integrator comprising:
an operational amplifier having at least one input terminal that receives an input signal;
a feedback mechanism operatively connected to said operational amplifier;
at least one capacitor coupled to said operational amplifier and said feedback mechanism;
a reset switch coupled to said at least one capacitor, said operational amplifier, and said feedback mechanism, wherein said reset switch resets said feedback mechanism; and
a single directional voltage-to-current converter coupled to said input terminal, wherein said single directional voltage-to-current converter translates a differential signal voltage only to a differential signal current.
2. The CT ΣΔADC of claim 1 , wherein said single directional voltage-to-current converter behaves as a one-directional resistor.
3. The CT ΣΔADC of claim 1 , wherein said integrator prevents current generation when there is a non-linear disturbance at said input terminal of said operational amplifier.
4. The CT ΣΔADC of claim 1 , wherein said single directional voltage-to-current converter clips an input current that exceeds a threshold value.
5. The CT ΣΔADC of claim 4 , wherein said threshold value is determined based on a modulation index of said CT ΣΔADC.
6. The CT ΣΔADC of claim 1 , wherein said single directional voltage-to-current converter provides a variable transconductance.
7. The CT ΣΔADC of claim 1 , further comprising:
a quantizer operatively connected to said integrator; and
a plurality of digital-to-analog converters (DACs) operatively connected to said integrator.
8. The CT ΣΔADC of claim 7 , wherein said single directional voltage-to-current converter provides capacitive input impedance to a previous stage of said integrator.
9. A continuous time sigma-delta analog-to-digital converter circuit (CT ΣΔADC) comprising:
an integrator comprising:
an operational amplifier having at least one input terminal that receives an input signal; and
at least one capacitor coupled to said operational amplifier;
a single directional voltage-to-current converter coupled to said input terminal, wherein said single directional voltage-to-current converter prevents current generation when there is a non-linear disturbance at said input terminal of said operational amplifier, and wherein said single directional voltage-to-current converter clips an input current that exceeds a threshold value;
a quantizer operatively coupled to said integrator to receive an output signal; and
at least one digital-to-analog converter (DAC) to receive an output signal from said quantizer and feed an input current to said integrator.
10. The CT ΣΔADC of claim 9 , wherein said single directional voltage-to-current converter behaves as a one-directional resistor.
11. The CT ΣΔADC of claim 9 , wherein said threshold value is determined based on a modulation index of said CT ΣΔADC.
12. The CT ΣΔADC of claim 9 , wherein said single directional voltage-to-current converter provides a variable transconductance.
13. The CT ΣΔADC of claim 9 , wherein said single directional voltage-to-current converter provides capacitive input impedance to a previous stage of said integrator.
14. A method of operation of a first integrator of a continuous time sigma-delta analog-to-digital converter (CT ΣΔADC), said first integrator comprising an operational amplifier, a voltage-to-current converter, and a capacitor, said method comprising:
translating a differential signal voltage only to a differential signal current, such that no current is generated when there is a non-linear disturbance at an input of said operational amplifier; and
adjusting a transconductance of said voltage-to-current converter to relax a dynamic range of said CT ΣΔADC.
15. The method of claim 14 , wherein said voltage-to-current converter behaves as a one-directional resistor.
16. The method of claim 14 , further comprising implementing said CT ΣΔADC using complementary metal-oxide-semiconductor (CMOS) means.
17. The method of claim 16 , wherein said voltage-to-current converter provides capacitive input impedance to a previous stage of said first integrator.
18. The method of claim 14 , further comprising clipping an input current when said input current exceeds a threshold value.
19. The method of claim 18 , wherein said threshold value is determined based on a modulation index of said CT ΣΔADC.
20. The method of claim 14 , further comprising effectively implementing a variable gain amplifier in front of said CT ΣΔADC.